During the production life of an oil or gas well, the production zone within the well is typically subjected to numerous treatments to enhance the lifetime of the well. Corrosion of metallic surfaces during such treatments is a prominent issue, as evidenced by surface pitting, embrittlement and loss of metal. Such metallic surfaces are typically composed of high alloy steels including chrome steels, duplex steels, stainless steels, martensitic alloy steels, ferritic alloy steels, austenitic stainless steels, precipitation-hardened stainless steels and high nickel content steels.
For instance, in such well stimulation techniques as pickling, acid washing, matrix acidizing and acid fracturing, the acidic nature of the treatment fluid causes the production or workover conduits in the well to encounter considerable acidic corrosion.
Further, aqueous fluids, such as those used in drilling and completion, have a high salt content which causes corrosion. Gases, such as carbon dioxide and hydrogen sulfide, also generate highly acidic environments to which metallic surfaces become exposed. For instance, corrosion effects from brine and hydrogen sulfide are seen in flow lines during the processing of gas streams. The presence of methanol, often added to such streams to prevent the formation of undesirable hydrates, further often increases the corrosion tendencies of metallic surfaces.
Further, naturally occurring and synthetic gases are often conditioned by treatment with absorbing acidic gases, carbon dioxide, hydrogen sulfide and hydrogen cyanide. Degradation of the absorbent and acidic components as well as the generation of by-products (from reaction of the acidic components with the absorbent) results in corrosion of metallic surfaces.
It is fairly common during such oilfield treatment processes to use a corrosion inhibitor to inhibit or prevent the corrosion of metallic surfaces, especially in acidic environments. Many conventional corrosion inhibitors used to reduce the rate of acid attack on metallic surfaces and to protect the tubular goods of the wellbore are becoming unacceptable in oilfield treatment processes. For instance, methanol has been found to deactivate many conventional corrosion inhibitors. In addition, many conventional corrosion inhibitors have become unacceptable due to environmental protections measures that have been undertaken.
There remains a need therefore for new, stable corrosion inhibitors which are effective for a wide variety of metallic surfaces.